The goal of this project is to better understand how structure and structural changes in the visual pigment rhodopsin are related to the physical physiological function of the protein. We investigate changes in the protein structure by selectively labeling rhodopsin with dye molecules whose adsorption and fluorescence spectra are sensitive to their immediate solvent or molecular environment. The probes we use to study rhodopsin are cyanine, Merocyanine and oxonol dyes that have reactive functional groups that permit covalent linkage of the probe to rhodopsin.